This application claims priority under 35 USC 119 from Japanese Patent Application No. 2003-80949, the disclosures of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to an inkjet recording head and an inkjet recording device.
2. Description of the Related Art
An inkjet recording device records text, images and the like on recording paper by reciprocating an inkjet recording head in a main scanning direction, conveying the recording paper in a sub-scanning direction, and selectively discharging ink droplets from a plurality of nozzles. A technology is well known in which an inkjet recording head discharges an ink droplet from a nozzle that communicates with a pressure chamber by applying pressure, via an oscillating diaphragm, to ink in the pressure chamber by using an actuator such as, for example, a piezoelectric element which converts electrical energy to mechanical energy.
In recent years, the trend for inkjet recording devices to get faster has intensified. Accordingly, inkjet recording heads which are capable of image formation over broader regions in shorter times have been produced by lengthening the inkjet recording heads, increasing the number of nozzles at each inkjet recording head, and arraying the nozzles in matrix patterns (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-334661).
When an inkjet recording head is lengthened and the nozzles are increased in number and arrayed in a matrix pattern as described above, a large number of piezoelectric elements arrayed in the matrix pattern are also required in accordance therewith. This large number of piezoelectric elements arrayed in the matrix pattern are formed by machining, for example, by sandblasting, a single piezoelectric plate (i.e., by machining a piezoelectric material such as a piezoelectric ceramic plate or the like, prior to preparation of the piezoelectric elements). Therefore, the longer the inkjet recording head, the longer the piezoelectric plate for forming the piezoelectric elements. However, making the piezoelectric plate longer and forming the large number of piezoelectric elements arrayed in the matrix pattern is problematic for manufacturing, and leads to a decrease in yields.
Accordingly, a technique has been considered in which a plurality of actuator units, at which the piezoelectric elements are formed, are connected in a row direction of the nozzles for lengthening. With such a structure, the large number of piezoelectric elements are formed so as to be divided up between a plurality of piezoelectric plates. In consequence, the decrease in yields does not result.
However, in a case in which a plurality of actuator units are thus joined for lengthening, problems may arise in assembly if there is no spacing at joining portions thereof. Accordingly, there is a technique in which a plurality of parallelogram-form actuator units are offset in the main scanning direction and a spacing L between the actuator units is assured (see, for example, JP-A No. 10-217452).
However, it is necessary to dispose the parallelogram-form actuator units to be offset in the main scanning direction in order to assure the spacing L between the actuator units. Consequently, the width in the main scanning direction of the inkjet recording head in which the actuator units are joined becomes larger in accordance with lengthening of the inkjet recording head (see FIG. 1 of JP-A No. 10-217452). As a result, the inkjet recording head becomes larger together with the length of the inkjet recording head.
Furthermore, because the nozzle rows are offset in the main scanning direction, it is necessary to offset ink drop discharge timings for each group of nozzles. As a result, the output of image data becomes more complicated.
The present invention has been devised in order to solve the problems described above, and an object of the present invention is to provide an inkjet recording head and inkjet recording device which improve production yields and enable lengthening of the inkjet recording head while assuring assembly characteristics and not increasing width of the inkjet recording head, and with which output of image data does not become more complicated in accordance with the increase in length.
In a first aspect of the present invention, an inkjet recording head includes: a nozzle plate in which nozzles which eject ink drops are formed; pressure chambers communicating with the nozzles; and actuators abutting at the pressure chambers, which at least one of increase and reduce pressures of ink in the pressure chambers. The inkjet recording head scans in a direction intersecting a conveyance direction of a recording medium and records an image at the recording medium with the ink drops ejected from the nozzles, and includes at least one nozzle row parallel to the conveyance direction of the recording medium. The inkjet recording head includes a plurality of nozzle groups structured by dividing up the nozzle row, the nozzles of the nozzle row include opposing nozzles which are disposed at a boundary between neighboring the nozzle groups which neighbor in the row direction of the nozzle row, the actuators include opposing actuators, which respectively correspond to the opposing nozzles, and actuators within the nozzle groups, which respectively correspond to nozzles neighboring the opposing nozzles in the row direction, and a separation between the opposing actuators disposed at the boundary is equal to or greater than separations between the opposing actuators and the corresponding actuators within the nozzle groups.
According to an inkjet recording head of the present invention, nozzle rows are divided up to structure a plurality of nozzle groups. Hence, the separation between opposing actuators, which respectively correspond to opposing nozzles disposed at a boundary between the nozzle groups which neighbor one another in the row direction of the nozzle rows, is provided so as to be equal to or greater than the separations between actuators within the nozzle groups, which respectively correspond to and are adjacent in the row direction to the nozzles disposed at the boundary, and the actuators corresponding to the nozzles disposed at the boundary.
According to the present aspect, the actuators are formed by machining for each group. When these actuator groups are joined to produce the inkjet recording head, there is naturally no problem with assembly characteristics. Furthermore, because the actuators are formed by machining from a plurality of actuator plates (an actuator material prior to machining of the actuators) which are short in accordance with the nozzle groups, yields are improved.
Further, because the nozzle rows are not offset even though the inkjet recording head is lengthened, the width of the inkjet recording head is not increased even though the number of actuators increases. Moreover, there is no need to offset the discharge timings for each nozzle group, and the output of image data will not become complicated.
In a second aspect of the present invention, an inkjet recording head includes: a nozzle plate in which nozzles which eject ink drops are formed; pressure chambers communicating with the nozzles; and actuators abutting at the pressure chambers, which at least one of increase and reduce pressures of ink in the pressure chambers. The inkjet recording head records an image over the width of a recording medium, which is being conveyed, with the ink drops ejected from the nozzles, and includes at least one nozzle row in a direction intersecting the conveyance direction of the recording medium. The inkjet recording head includes a plurality of nozzle groups structured by dividing up the nozzle row, the nozzles of the nozzle row include opposing nozzles which are disposed at a boundary between neighboring the nozzle groups which neighbor in the row direction of the nozzle row, the actuators include opposing actuators, which respectively correspond to the opposing nozzles, and actuators within the nozzle groups, which respectively correspond to nozzles neighboring the opposing nozzles in the row direction, and a separation between the opposing actuators disposed at the boundary is equal to or greater than separations between the opposing actuators and the corresponding actuators within the nozzle groups.
According to the inkjet recording head of the present aspect, effects similar to those provided by the first aspect are provided. Further, according to the present aspect, the inkjet recording head is fixed but can record images over the width of the recording medium that is being conveyed, and thus an inkjet recording head capable of high-speed printing is provided.
In a third aspect of the present invention, arrangement forms of the nozzles of the nozzle groups of an inkjet recording head of an aspect described above include, if straight lines are taken between the nozzles disposed at outer edges of the nozzle groups, at least one of a triangular form, a parallelogram form and a trapezoid form.
In a fourth aspect of the present invention, the arrangement forms of the nozzle groups of the above-described third aspect include a combination of forms including at least one of the triangular form, the parallelogram form and the trapezoid form.
In a fifth aspect of the present invention, a nozzle pitch of the nozzles of the nozzle groups in the row direction is the same as a spacing between the nozzles disposed at the boundary between the neighboring nozzle groups.
According to an inkjet recording head of the present aspect, results the same as in the aspects described above are provided. Further, because the nozzle pitch in the row direction of the nozzle row of the nozzle groups and the spacing between the opposing nozzles disposed at the boundary of the neighboring nozzle groups in the row direction of the nozzle row are the same, the inkjet recording head is not enlarged in the row direction of the nozzle rows.
In a sixth aspect of the present invention, the opposing actuators of an inkjet recording head of an aspect described above, borders of which oppose the boundary between the neighboring nozzle groups, include point symmetry.
According to the present aspect, the actuators whose borders oppose the boundary of the neighboring nozzle groups have a structure with point symmetry. Thus, a gap is opened up between the opposing actuators. Accordingly, effects the same as in the first to fifth aspects described above are provided.
In a seventh aspect of the present invention, the opposing actuators of an inkjet recording head of an aspect described above, borders of which oppose the boundary between the neighboring nozzle groups, include line symmetry.
According to the present aspect, the actuators whose borders oppose the boundary of the neighboring nozzle groups have a structure with line symmetry. Thus, a gap is opened up between the opposing actuators. Accordingly, effects the same as in the first to fifth aspects described above are provided.
In an eighth aspect of the present invention, the inkjet recording head of the first aspect has an actuator unit for each nozzle group, the actuator unit being structured to include at least the pressure chambers and the actuators respectively corresponding to the nozzles constituting the nozzle groups.
Because, according to the present aspect, an actuator unit structured to include at least the pressure chambers and the actuators respectively corresponding to the nozzles constituting the nozzle group is provided for each nozzle group, actuator characteristics tests for predicting ink drop discharge characteristics can be carried out on each actuator unit prior to assembly. Hence, the occurrence or absence of failures at each actuator unit, characteristics thereof and the like can be found. Therefore, by selecting the actuator units, co-ordinating the characteristics of the actuator units and assembling the same, ink droplet discharge characteristics of the inkjet recording head can be made more uniform.
In a ninth aspect of the present invention, each nozzle group of an inkjet recording head of the above-described eighth aspect is provided with an ink discharge unit including at least the nozzle plate and the actuator unit.
According to the present aspect, the ink discharge unit including at least the nozzle plate and the actuator unit is structured at each nozzle group. Hence, ink drops can be discharged at each ink discharge unit.
Further, because, as described above, the separation in the row direction of the nozzle row between the opposing actuators corresponding to the opposing nozzles disposed at the boundary between the neighboring nozzle groups is relatively large, the ink discharge units can be associated to structure the inkjet recording head without shifting the nozzle rows.
Thus, the inkjet recording head can be lengthened without increasing the width of the inkjet recording head. Further, there is no need to offset the discharge timings at each ink discharge unit, and an increase in complexity of the output of image data is avoided. Moreover, in cases in which problems arise, the ink discharge units can be individually replaced.
In a tenth aspect of the present invention, the actuators of each nozzle group of an inkjet recording head of an aspect described above are disposed with an orientation the same as the actuators disposed at the boundary of the nozzle group.
The actuator units and the ink discharge units have consistent forms. Therefore, in the present aspect, one kind of the actuator units and one kind of the ink discharge units may be associated, and there is no need to prepare two kinds of actuator unit and ink discharge unit. Thus, production costs will not rise.
In an eleventh aspect of the present invention, positions of the actuators within each nozzle group include point symmetry, with a center of the nozzle group as the point of symmetry thereof.
Because, according to the present aspect, the positions of the actuators within the nozzle group include point symmetry with the center of the nozzle group as the point of symmetry, the inkjet recording head can be further lengthened in the row direction. Therefore, in a case in which it is desired to increase the number of nozzles, this can be easily implemented by joining actuator units and ink discharge units in the row direction of the nozzles. Further, given that the actuator units and ink discharge units have the same shapes, the one kinds of actuator units and ink discharge units may be associated. Thus, production costs will not rise.
In a twelfth aspect of the present invention, the actuators include piezoelectric elements for converting electrical energy to mechanical energy.
In a thirteenth aspect of the present invention, the actuators include heat-generating resistors which pressurize the ink in the pressure chambers by heating and causing bubbling.
In a fourteenth aspect of the present invention, an inkjet recording device employs an inkjet recording head of one of the first to thirteenth aspects described above.
In an inkjet recording device based on the present aspect, the width of the inkjet recording head is not increased. Therefore, the inkjet recording device is not made larger.